Field of the Invention
The invention relates in general to an echo discriminating device and method, and more particularly to an echo discriminating device and method capable of discriminating whether an echo occurs in a communication channel.
Description of the Related Art
In some communication channels, radio waves from a transmitting end are propagated non-directionally, and arrive at a receiving end via many different paths. Thus, the receiving end receives more than one signal. Due to different propagation paths, these different signals have different attenuation and delay levels. Such attenuation and delay result in an unstable data transmission rate and form multipath propagation effects. Further, when the transmitting end and the receiving end move relatively to each other, different available propagation channels on the moving paths of the transmitting and/or receiving end are obtained, such that not only the amplitude and phase of transmitted signals are varied and delayed, but also the number of signals received by the receiving end is changed. In short, various changes in the received signals are incurred due to transmission delay caused by multipath propagation. Further, multipath propagation may also be explained as follows. When a pulse signal is transmitted from a transmitting end, if a plurality of analyzable paths are caused by a multipath effect, a receiving end will receive signals coming from different paths but containing the same information. Each of the analyzable paths has a predetermined delay, which results in inter-symbol interference (ISI), as an echo in a valley, hence degrading the transmission quality. Therefore, it is essential that an echo be correctly discriminated and eliminated by appropriate equalization and signal processing.
In known technologies, a receiver circuit generates a channel response by a channel estimator, and observes the estimated channel response in the time domain to determine conditions of the channel. More specifically, an issue of known technologies is that, because the channel response is changeable with time, when signal changes of the channel response are observed in the time domain, the receiving end may not be able to identify actual changes in the channel response or further changes due an echo effect caused by multipath channels. Thus, an incorrect communication mechanism may be adopted, hence degrading the performance of communication transmission.